It is known that high-pressure hoses containing various metal reinforcing plies are widely used by the industry in different fields. These hoses are usually characterized by a polymer-based, flexible innermost layer, the so called liner, functioning as a sealing, fluid-retaining isolating layer between the fluid transported in the hose and the other layers of the hose. As for the material of the liner, it can be made of thermoplastic or cross-linked plastic, most frequently, however, of vulcanized rubber.
As it is well-known high-pressure hoses contain reinforcing plies as load bearing elements. These also can be made of various materials and be of various designs. According to the design of the reinforcing plies there are hoses in which the reinforcing plies are formed by braided steel wires of circular cross section. Such hoses are described for instance in the Standard SAE J 517.
In other hoses the reinforcing plies are made of helically wound steel wires or cables; such hoses are the ones according to API Specification 17K elaborated by American Petroleum Institute (API) and the corresponding ISO 13628-10 which are bonded (rubber) hoses, or the reinforced flexible hoses, according to Hungarian Patent No. 198 781 (corresponding to No. U.S. Pat. No. 4,860,798). The latter relates to flexible hoses reinforced by wire plies, wherein the wires are laid spirally, at least in two layers, and the hoses may contain rings which are more rigid than the fibres or a low-pitch helix, as well.
In yet other hoses the reinforcing plies can be steel profiles and spirally wound flat steel tendons; such designs are known for instance from API Specification 17J related to requirements for unbonded (plastic based) hoses.
For providing protection against different impacts high-pressure hoses generally contain an elastic outer layer, the so called cover, further they can comprise a number of other elements, such as an inner flexible stripwound, an outer armouring, a rigid helix, steel rings, layers providing flame-resistance etc. All these elements and possibilities including the requirements of special application areas are well-known to those skilled in the art.
According to prior art the flexible high-pressure hoses are connected to each other or to rigid pipelines by metal couplings. The critical point of the hose-lines is the connection between the flexible hose and the rigid coupling, which has to provide sealing between the elastic liner and the rigid coupling, besides of the mechanical bond. Several designs are known for the coupling. For instance according to the designs described in the Hungarian Patent Nos. 168 837, 218 344, and 224 141 and corresponding U.S. Pat. No. 6,938,932 the metal coupling is bonded to the reinforcing plies by adhesive resin and the sealing between the rubber and the coupling is formed by metal-to-rubber bond. In unbonded hoses too the coupling is fixed by adhesive bonding, but the sealing is produced mechanically. Examples are found in the Standard API RP 17B.
According to another, well-known fixing way in practice the metal coupling is fixed to the hose-end by swaging as it can be known for instance from the International Patent Application WO 0242672 and the Hungarian Patent No. 176 336.
When hoses are connected to each other, the common disadvantage of the above referred designs is that at least three potential leakage paths can be formed in the coupled hose-lines; namely between the two couplings connected to each other, and between the corresponding metal couplings and the elastic liner. The number of these potential leakage places is multiplied by the number of the coupled hose-pieces (corresponding to the number of the connections). The actual situation is often worse than this, because usually the coupling device itself consists of two or more parts and leakage can be developed between these parts too.
The above detailed disadvantages can explain the reluctance of the users to couple hoses into lines or the fact for example that laying of such lines is often not allowed in the case of high-pressure submarine lines for reasons of environment protection.
Another considerable disadvantage is that at the location of the connection a relatively long, rigid section is formed, the dimension of which corresponds to that of the two couplings, and during the use this makes difficult or impossible to wind the hoses to a reel of reasonable size.